What does the thyroid do in dogs?
The thyroid is a gland located in the neck that plays an important role in many functions throughout the body. It helps regulate weight, metabolism, and energy levels. When the thyroid is not functioning properly, we often begin to notice changes in these areas.
Is hyperthyroidism common in dogs?
Hyperthyroidism, where the body produces too much thyroid hormone, is actually very uncommon in dogs. We see it much more frequently in cats. In dogs, we primarily diagnose hypothyroidism, where the body produces too little thyroid hormone.
What dogs are most likely to develop hypothyroidism?
Hypothyroidism can occur in any dog, but we most commonly diagnose it in middle-aged dogs. There is not a strong breed predisposition, so it is something we consider in many different patients.
What causes hypothyroidism in dogs?
There are two main causes of hypothyroidism in dogs. The most common is an autoimmune disease in which the body gradually attacks the thyroid gland, causing it to produce less thyroid hormone over time. The other is degeneration of the thyroid gland itself. In these cases, the gland gradually loses its ability to produce enough thyroid hormone, even without an immune-mediated cause.
What are the most common symptoms of hypothyroidism in dogs?
When I start thinking about hypothyroidism, I often picture a dog that is gaining weight despite no changes in diet. That's usually a big clue. Owners commonly tell me, "I feel like they're gaining weight, but we haven't changed their food or given them more treats." These dogs are often more tired than usual, have lower energy levels, and may seek out warm places to rest. We can also see thinning of the hair coat, especially on the tail and flanks, along with skin changes. Some dogs also experience recurrent ear infections and skin infections.
Can thyroid disease affect a dog's behavior or mood?
Yes, it can. Dogs with thyroid disease may seem sleepier or less active than usual, but it is not typically a true personality change. Instead, their thyroid is not functioning properly, so they simply don't have the energy levels they normally would. It's more of a change caused by the disease than a change in their personality.
How do veterinarians diagnose thyroid disease in dogs?
We always start with a thorough physical examination and a detailed history from the owner to identify any signs of thyroid disease. Laboratory testing is an important part of the diagnostic process, and we rely heavily on blood work to help confirm the diagnosis.
Can thyroid tests ever be misleading?
Yes. Thyroid test results can sometimes be misleading because thyroid hormone levels may be suppressed for reasons other than thyroid disease. While many people think we only check a total T4 level, if a dog is showing symptoms of hypothyroidism and has a low thyroid value, we'll often run a more comprehensive thyroid panel. This typically includes a free T4, ideally measured by equilibrium dialysis, and sometimes a TSH test. We interpret these results alongside your dog's clinical signs to make the most accurate diagnosis possible.
How is hypothyroidism in dogs treated?
Hypothyroidism in dogs is treated with an oral medication called levothyroxine. Depending on the individual dog and dosage, it may be given once or twice a day. In most cases, this is a lifelong medication, much like thyroid hormone replacement in people with hypothyroidism.
How do you monitor treatment for hypothyroidism?
After starting levothyroxine, we typically recheck thyroid levels about one month later to make sure the dosage is appropriate. Many dogs show improvements in their energy level and overall well-being within about two weeks of starting treatment, although improvements in the hair coat and skin may take a little longer.
What happens if hypothyroidism goes untreated?
If hypothyroidism goes untreated, dogs can experience a poor quality of life due to ongoing lethargy, low energy levels, continued weight gain, and an inability to regulate their metabolism normally. Early diagnosis and treatment can help dogs return to feeling much more like themselves.
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